With BSs (Broadcasting Satellites) starting digital broadcasting, and with DVDs (digital versatile disks) in widespread use, video apparatuses increasingly handle digital video signals.
The digital video signal, because of the large data size thereof, is typically compression encoded in a predetermined method before being transmitted to another apparatus or stored on a recording medium, or transmitted to the other apparatus and stored on the recording medium at the same time. MPEG 2 (Moving Picture Experts Group 2) is currently well known as a standard compression encoding method. In MPEG2, a digital video signal is compression encoded using predictive encoding based on DCT (Discrete Cosine Transform) and motion compensation, and variable length encoding is further used to increase data compression rate.
The above-mentioned BS digital broadcasting uses MPEG2 to compression encode moving image data in interlace scanning of HDTV (High Definition Television). Digital video signals recorded on DVD (Digital Versatile Disk) sold in package medium are typically interlace scanned, and compression encoded using MPEG2.
In MPEG2, an image for use in predictive encoding is adaptively switched between frame and field. DCT has a mode in which macro block serving as a unit of encoding is adaptively switched between frame and field. In MPEG2, the use of encoding means for interlace moving image has successfully increased encoding efficiency.
In professional applications such as broadcasting or production, compression encoding focusing on editing, such as DV or DVC-Pro, is used. Such compression encoding has intra picture (I picture) only as in-frame encoding, and does not perform inter-frame compression. A frame-by-frame editing operation essential for professional applications can thus performed without degrading image quality. In the above-described MPEG2, encoding free from predictive encoding is possible, and the frame-by-frame editing operation can thus be performed.
Patent Document 1 discloses an encoding and decoding method for compression encoding efficiently a digital video signal while editing the digital video signal by frame in 525/60P system (525 lines/frame, 60 frames/second progressive system) or 1080/60P system (1080 lines/frame, 60 frames/second progressive system). In accordance with the Patent Document 1, an addition signal and a difference signal of an image signal between frames are retrieved and encoded, and a ratio of an encoding bit rate of the addition signal and an encoding bit rate of the difference signal are controlled.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-104694